1. Field
The present disclosure relates generally to electronics, and more specifically to transmitters and receivers.
2. Background
In a radio frequency (RF) transceiver, a communication signal is developed, upconverted, amplified and transmitted by a transmitter and is received, amplified, downconverted and recovered by a receiver. In the receiver, the communication signal is typically received and downconverted by receive circuitry including a filter, an amplifier, a mixer, and other components, to recover the information contained in the communication signal. A single transmitter or receiver can be configured to operate using multiple transmit frequencies and/or multiple receive frequencies. For a receiver to be able to simultaneously receive two or more receive signals, the concurrent operation of two or more receive paths is used. Such systems are sometimes referred to as “carrier-aggregation” (CA) systems. The term “carrier-aggregation” may refer to systems that include inter-band carrier aggregation (Inter-CA) and intra-band carrier aggregation (Intra-CA). Intra-CA refers to the processing of two or more separate (either contiguous or non-contiguous) carrier signals that occur in the same communication band. The carrier aggregated RF signal is typically down-converted using one or more distinct local oscillator (LO) frequencies, which generally employs a low noise amplifier (LNA) having a single RF input and multiple RF outputs to process the multiple carriers present in the Intra-CA RF signal.
State-of-the-art transceiver design focuses on reducing the total number of pins to be cost competitive. Such trends will reduce the number of power supply and ground pins, and will likely drive the circuit architecture toward using shared low dropout (LDO) voltage regulators for reducing the number of power pins needed to power the various amplifiers in the transceiver. State-of-the-art transceiver design focuses on integrating more concurrently operating systems which will aggregate coupling between and among these systems and demand innovative circuit and signal isolation strategies.
The use of an LDO power supply and its shared power distribution network dictates that the isolation between the LDO for a first carrier, CA1 and the LDO for a second carrier CA2 be robust. Normally, an LDO and related shared power distribution network do not provide good isolation at high frequencies. Therefore, a signal isolation solution that allows an LDO power system to be employed, without reliance on decoupling capacitors to improve the isolation at high frequencies is needed.